For may years it has been common practice to stiffen or tension sails by means of battens which extend generally horizontally across the sail. The battens are housed in pockets in the sail and may be forced into the pocket from an open end of the pocket at the trailing edge of the sail, to provide extra tension in the sail. The batten may be held tightly in the pocket by a strap and friction buckle arrangement.
In some arrangements, the battens extend across the full width of the sail and the end of the batten at the leading edge of the sail may be located on the mast. In sailboards, such a system has been found to be particularly useful in enhancing the performance of the sail. The user is able to induce or enhance the camber in the sail near the mast and the system may provide for a smooth, aerodynamic transition from the luff pocket of the sail, which encircles the mast, to the main body of the sail.
Examples of systems used in sailboards are seen in U.S. Pat. No. 4,625,671 (Nishimura), U.S. Pat. No. 4,649,848 (Belvedere), and U.S. Pat. No. 4,686,921 (Magnan). In all these systems the coupling member or socket, which locates the batten end at the mast and allows it to pivot about the mast, is located in the luff pocket. Generally several coupling members are used per sail, each locating a respective batten end. In practice, such systems complicate the rigging process and may require a lot of adjustment to keep them functioning properly.
Main purposes of the coupling member are to help form a stable leading edge, to induce draft in the sail, and to help stabilise that draft so that the sail maintains its aerodynamic foil shape in gusts, when accelerating, or at high speed. The systems described above, using a plurality of coupling members, can result in a foil shape which is too rigid, making the sail difficult to depower, for example by luffing, and they may inhibit rotation of the sail about the mast.